The invention relates to a multi-spindle automatic lathe with a number of workpiece spindles which are disposed on the spindle circle of a spindle drum that is rotatably displaceable.
In multi-spindle automatic lathes it is usual to drive the workpiece spindles mounted in the spindle drum from a central drive shaft via a central driving wheel. In the absence of further measures all the spindles have the same speed and if they are to rotate at different speeds it is necessary to provide several central driving wheels of different diameters, which wheels are either arranged on several coaxial hollow shafts or drive the spindles by means of gearwheels and clutches.
In order to be able to drive individual workpiece spindles at different speeds a multi-spindle automatic lathe is known (DE-OS No. 23 51 557) in which separate drives which are arranged in fixed positions behind the spindle drum and, in the working positions of the spindles, can be connected with the spindles by means of clutches which comprise a driving part connected with the output shaft of a drive means and a driven part connected with a specific spindle. The spindles can be connected with their rear ends direct with the output shaft of separate gear units. The gear units have multi-step reduction gears by means of which specific ratios, and therefore only fixed, though differing, speeds of the spindles can be achieved. However, this known construction of automatic lathe particularly suffers from the drawback that the rear ends of the spindle are not free, so that the arrangement cannot be used for automatic bar machines in which the bar material is supplied from the rear through the spindles to the workpiece spindles of hollow form. In use in automatic chucking lathes the clamping units for the chuck cannot be mounted as usual on a spindle end, as the clutch is situated there.
An object of the invention is to provide a multi-spindle automatic lathe in which it is possible to drive all spindles at the speed that is most suitable for the machining operation carried out on them at the particular time and that can also be varied during machining. A further object of the invention is to provide a multi-spindle automatic lathe in which it can be ensured that the rear ends of the spindles remain free for the workpiece feed.